Photographic element and method of producing the same



PatentedJuly 14, 1942 I UNITED STATES PATENT OFFICE 2,289,803,

PHOTOGRAPHIC ELEMENT AND METHOD OF PRODUCING THE SAME Willard D. Peterson, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application May 22,1940, Serial No. 336,581. In Great Britain May 22, 1939 Claims. (01. 95-?) It is well known to produce images by developing a silver salt image in presence of a coupling component, by which I mean a compound which, during production of the silver image by the photographic development, couples with the oxidation products of the developing agent where they are formed. If such coupling components are added to the developer solution, or incorporated in the emulsion layer, the dye which is thus formed by coupling is deposited'in the.gela-' tine or other silver halide carrier adjacent to the metallic silver grain. It is desirable that the dyes formed should not readily wander from the place of formation and it is accordingly desirable that they should be insoluble in water.

They are probably not physically attached to the silver grain. At all events, the silver may be subsequently bleached out of 'the carrier layer leaving a pure dye image.

When the coupling components are lncorporated in the emulsion it is important that they should not wander or diffuse to any substantial extent during processing. If an emulsion'c'ontainingva coupling component is adjacent to, or near to, another emulsion not containing a coupling component or containing a different coupling component it-is equally important that diffusion or wandering of the coupling component or any of them should not take place at any time prior to the processing, e. g. during coating.

Numerous proposals have been made to produce coupling components which will not wander or diffuse from the emulsions in which they are incorporated. In some of these proposals attempts were made soas to alter the coupling components that they would have an amnity for gelatine, e. g. by the introduction of groups said I to be substantive. In others, groups ofhigh molecularweight were introduced into the coupling components. Although it has been proposed to cause coupling components to be absorbed to the silver halide g'rainswvith the object of avoiding diffusion, most of the methods proposed have involved chemical synthesis of a more complex coupling component from a simpler coupling component. When this is done there is usually an undesirable tendency for the absorption range of the resulting dye to become wider and the absorption curve to become flatter resulting in less pure dye images.

It has now been found that coupling components which ordinarily have a tendency to diffuse when incorporated in gelatino-silver halide emulsions'exhibit much less tendency to diffuse if there are also incorporated in the emulsions with them substances of high molecular weight which can readily dissolve them. These 'substances, which may be termed modifiers are inert additions to, or diluents for, the photographic. emulsion. Owing to their high solvent action for the coupling component they associate themselves persistently with these coupling com ponents and on account of their own high molecular weight they show little tendency to diffuse through the gelatine. Accordingly, the cou-v pling components are, in effect, fixed in their position. by themodifiers." The modifiers do not combine chemically with the coupling components and accordingly the chemical composition of the coupling components and of the dyes formed therefrom are substantially unaffected thereby.

Examples of suitable modifiers are; .polyvinyl alcohol, polyvinylphthalate, glycerolphthalate, cellulose acetate phthalate, and gum arabic. These products are soluble in water or dilute alkali and their solutions mix very readily with aqueous gelatin. solutions. It has been found that the refractive indices of these solutions and of the gelatin solution are nearly the same, so that there is very little, if any, opaqueness or haziness produced through incorporating them in emulsions.

By the way of example, the following experiment indicates the effect of the present invention:

To one hundred grams of a gelatino-silver bromide emulsion is added 0.15 gram of the sodium salt of para-phenylbenzoyl-acetonitrile. The gelatin emulsion is hardened with a small quantity of formalin. The emulsion is coated onto a support, set, and allowed to dry thoroughly, and a second coating of silver bromide which contains no coupling component is coated over the first layer of emulsion. Upon processing the exposed emulsion with a suitable solution of p aminodiethyl-aniline, a magenta dye is generated throughout both emulsion layers (indicating diffusion of the coupling component into the upper layer) If, however, a quantity of polyvinyl alcohol (10 per cent of the weight of the gelatin in the emulsion) is added to the silver bromide emulsion not contain the polyvinyl alcohol.

containing the coupling component, and the emulsion i hardened in exactly the same manner, the final dye image is almost entirely in the lower layer, indicating only slight diffusion of the coupling component. There appears to be improved dispersion of the dye (less scatter) of the dyes image than in the emulsion which does This dispersion of the dye is chiefly dependent upon the degree of dispersion of the modifier or "nondiffusion solvent (polyvinyl alcohol in this case) in the gelatin.

Although the modifiers given by way of example are water-soluble or alkali-soluble resins, partially water-soluble.resins or polymers may be used.

The modifiers" may also be employed for redesirable. Where I refer in the claims to "dye compounds I intend to include such dyes as well as couplers and dye intermediates.

Thus, the invention may be applied to photo graphic elements having a plurality of emulsion layers on a single support for the purpose of retarding the diffusion of a coupling component and/ or a sensitizing dye and/or a filter dye from one layer to another or to a photographic element having mixed emulsions on a support for the same purpose or to photographic elements having filter layers or antihalation layers or the like for the purpose of retarding the diffusion of filter dyes or the like into neighboring sensitive layers. It is well lmown that in multi-color photography difiiculty is encountered through the wandering from one emulsion to another of color sensitizers or filter dyes or through the wandering of filter dyes from filter layers to sensitized emulsions,

whether coupling components are present in such emulsions or not. The present invention provides a means for retarding such diffusion.

The invention is not limited to the specific examples described herein, but is to be taken as including all modifications coming within the scope of the appended claims.

I claim: I

1. The method of preventing diffusion of color couplers having a reactive group selected from the class consisting of phenolic hydroxyl and re- 2. The method of preventing diffusion of color couplers incorporated in gelatino-silver halide emulsion layers, which comprises mixing the coupler with the emulsion and an appreciable amount of a water-soluble polyvinyl resin.

3. The method of preventing difiusion of color couplers incorporated in gelatino-silver halide emulsion layers, which comprises mixing the coupler with the emulsion and an appreciable amount of polyvinyl alcohol.

4. The method of preventing diffusion of color couplers incorporated in gelatino-silver halide emulsion layers, which comprises mixing the coupler with the emulsion and an appreciable amount of a phthalic acid ester of an aliphatic polyhydroxy compound.

5. The method of preventing diffusion of color couplers incorporated in gelatino-silver halide emulsion layers, which comprises mixing the coupler with the emulsion and an appreciable amount of polyvinyl phthalate.

6. A multi-layer photographic element comprising ,at least one gelatino-silver halide emulsion layer, which contains a color coupler having a reactive group selected from the class consisting of phenolic hydroxyl and reactive methylene, rendered non-diffusing by mixing it with the emulsion and an appreciable amount of a watersoluble synthetic resin.

7. A multi-layer photographic element comprising at least one gelatino-silver halide emulsion layer, which contains a color coupler having a reactive group selected from the class consisting of phenolic hydroxyl and reactive methylene, rendered non-diflusing by mixing it with the emulsion and an appreciable amount of awatersoluble polyvinyl resin.

8. A multi-layer photographic element comprising at least one gelatino-silver halide emulsion layer, which contains a color coupler rendered non-diffusing by mixing it with the emulsion and an appreciable amount of polyvinyl alcohol.

9. A multi-layer photographic element coma prising at least one gelatino-s'flver halide emulactive'methylene, which couple with the oxidasion layer, which contains a color coupler rendered non-diffusing by mixing it with the emulsion and an appreciable amount oi. a phthalic acid ester of an aliphatic polyhydroxy compound.

10. A multi-layer photographic element comprising at least one gelatino-silver halide emulsion layer, which contains a color coupler rendered non-diflusing by mixing it with the emulsion and an appreciable amount of polyvinyl Bl phthalate.

W'ILLARD D. PETERSON. 

